What is the difference between MySQL Server and MySQL Client

In Ubuntu I normally install both but what are the differences between the client and server for MySQL. As a bonus, when a new statement mentions that it needs MySQL 5.x does it mean the client, the server or both. For example this link https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html mentions that it need 5.7.x for it to support json_extract, does this mean the client, server or both need to be 5.7.x